Observation of the decay ${\Lambda }_b^0\to {\chi }_{c1}p{\pi }^{-}$

Abstract

The Cabibbo-suppressed decay ${\Lambda }_b^0\to {\chi }_{c1}p{\pi }^{-}$ is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6fb${}^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13TeV. Evidence for the ${\Lambda }_b^0\to {\chi }_{c2}p{\pi }^{-}$ decay is also found. Using the ${\Lambda }_b^0\to {\chi }_{c1}p{K}^{-}$ decay as normalisation channel, the ratios of branching fractions are measured to be $$\begin{array}{rclcccc}\frac{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c1}p{\pi }^{-})}{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c1}p{K}^{-})}& =& (6.59\pm 1.01\pm 0.22)\times 10^{-2},\frac{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c2}p{\pi }^{-})}{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c1}p{\pi }^{-})}& =& 0.95\pm 0.30\pm 0.04\pm 0.04,\frac{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c2}p{K}^{-})}{\mathcal{B}({\Lambda }_b^0\to {\chi }_{c1}p{K}^{-})}& =& 1.06\pm 0.05\pm 0.04\pm 0.04,\end{array}$$ where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of ${\chi }_{c1,2}\to J/\psi \gamma$ decays.

arXiv comment19 pages, 3 figures, All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-003.html (LHCb public pages)". arXiv admin note: text overlap with arXiv:1806.08084

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